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Andru [333]
3 years ago
11

The time for a professor to grade an exam is normally distributed with a mean of 16.3 minutes and a standard deviation of 4.2 mi

nutes. What is the probability that a randomly selected exam will require more than 15 minutes to grade
Mathematics
1 answer:
dem82 [27]3 years ago
8 0

Answer:

62.17% probability that a randomly selected exam will require more than 15 minutes to grade

Step-by-step explanation:

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean \mu and standard deviation \sigma, the zscore of a measure X is given by:

Z = \frac{X - \mu}{\sigma}

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

\mu = 16.3, \sigma = 4.2

What is the probability that a randomly selected exam will require more than 15 minutes to grade

This is 1 subtracted by the pvalue of Z when X = 15. So

Z = \frac{X - \mu}{\sigma}

Z = \frac{15 - 16.3}{4.2}

Z = -0.31

Z = -0.31 has a pvalue of 0.3783.

1 - 0.3783 = 0.6217

62.17% probability that a randomly selected exam will require more than 15 minutes to grade

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We have a jar of coins, all pennies and dimes. All together, we have 309 coins, and the total value of all coins in the jar is $
Vinvika [58]

There are 130 pennies in the jar

Step-by-step explanation:

We have a jar of coins

  • All coins are pennies and dimes
  • There are 309 coins in the jar
  • The total value of all coins in the jar is $ 19.2

We need to find the number of pennies in the jar

Assume that there are p pennies and d dimes in the jar

∵ There are p pennies and d dimes in the jar

∵ There are 309 coins in the jar

∵ All the coins in the jar are pennies and dimes

∴ p + d = 309 ⇒ (1)

∵ The total value of all coins in the jar is $ 19.2

∵ $1 = 100 cents

∴ $19.2 = 19.2 × 100 = 1920 cents

∵ 1 penny = 1 cent

∵ 1 dime = 10 cents

∴ p + 10 d = 1920 ⇒ (2)

Now we have system of equations, we can solve them to find p

∵ p + d = 309 ⇒ (1)

∵ p + 10 d = 1920 ⇒ (2)

- Multiply equation (1) by -10 to eliminate d

∵ (-10)(p) + (-10)(d) = (-10)(309)

∴ -10 p - 10 d = -3090 ⇒ (3)

Add equations (2) , (3)

∴ -9 p = -1170

- Divide both sides by -9

∴ p = 130

There are 130 pennies in the jar

Learn more:

You can learn more about the system of equations in brainly.com/question/3739260

#LearnwithBrainly

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Step-by-step explanation:

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